Heat exchange method using fluorinated compounds having a low gwp

ABSTRACT

The present invention relates to a method for exchanging heat with an object said method comprising using a heat transfer fluid wherein said heat transfer fluid comprises one or more chemical compounds having the general formula (I) wherein: —R f  can be any C 1 -C 10  fluorinated linear or branched carbon chain which can be partially or fully fluorinated, and can comprise O or S atoms, —X, Y and Z can be independently selected from halogens or hydrogen, with the provision that at least one of X, Y or Z is a halogen.

TECHNICAL FIELD

The present invention relates to a method for exchanging heat with anobject using compositions comprising selected fluorinated compoundshaving low GWP as heat transfer fluids.

BACKGROUND ART

This application claims priority to EP Appl. No. 19163552.3 filed on 18Mar. 2019, the whole content of this application being incorporatedherein by reference for all purposes.

Heat transfer fluids are known in the art for applications in heatingand cooling systems; typically, heat transfer fluids include water,aqueous brines, alcohols, glycols, ammonia, hydrocarbons, ethers andvarious halogen derivatives of these materials, such aschlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HFCs),(per)fluorinated polyethers (PFPEs) and the like.

Heat transfer fluids are used to transfer heat from one body to another,typically from a heat source to a heat sink so as to effect cooling ofthe heat source, heating of the heat sink or to remove unwanted heatgenerated by the heat source. The heat transfer fluid provides a thermalpath between the heat source and the heat sink; it may be circulatedthrough a loop system or other flow system to improve heat flow or itcan be in direct contact with heat source and heat sink. Simpler systemsuse simply an airflow as heat transfer fluid, more complex system usespecifically engineered gases or liquids which are heated orrefrigerated in a portion of the system and then are delivered inthermal contact with the destination.

Computing equipment such as computers, servers and the like generatesubstantial amounts of heat. Massive developments concentrating a largenumber of computers operating in shared locations such as server farmsare getting more and more common. The industry of server farms, bitcoinmining farms and other supercomputing applications is growing extremelyfast. A key factor in determining the building strategy of suchinstallations is a control system which allows exchanging heat with suchcomputing equipment. This system, often called “thermal managementsystem”, is typically used for cooling the computing equipment duringits operation, but it can also be used for heating e.g. when starting upa system in a cold environment. Air is still the most commonly usedfluid which however has the drawback to require large air gaps betweenelectronic boards, which causes the installation to have very largefootprints. Air cooling also requires massive air conditioning enginesand their energy consumption is extremely high and represents asignificant portion of the running costs for such installations.

Recently, solutions for thermal management of servers based on the useof heat transfer fluids, especially liquid heat transfer fluids aregetting a lot interest because they are both energy efficient (use lessenergy than traditional air conditioning systems) and allow to pack moreservers, processors and circuit boards in a smaller space.

Other important specialized applications for heat transfer fluids can befound e.g. in the semiconductor industry (TCUs, thermostatic baths,vapor phase soldering) and in the batteries industry especially in thevehicle battery industry for their thermal management systems.

A variety of heat transfer fluids exist which are used industrially invarious application, however the choice of an appropriate fluid can becritical in some applications. Several of the heat transfer fluidscommonly used in the past are no longer viable because of their toxicity(ammonia, ethylene glycol), others have been phased out due to theirenvironmental profile because they are not biodegradable and/or becausethey are considered to be detrimental to the earth ozone layer and/or toact as greenhouse gases if dispersed in the environment.

Fluorinated liquids are very effective heat transfer fluids. Commercialproducts exist such as Solvay's Galden and 3M's Fluorinert: these areliquid polymers which are dielectric, have a high heat capacity, a lowviscosity and are non-toxic and chemically inert so they can get indirect contact with electronic boards and also do not chemicallyinteract with most materials. A drawback associated with thesefluorinated fluids used so far is their high GWP value.

GWP (Global Warming Potential) is an attribute which can be determinedfor a given chemical compound which indicates how much heat a givengreenhouse gas can entrap in the atmosphere (considering “1” as thereference value for CO₂) and is calculated over a specific interval oftime, typically 100 years (GWP₁₀₀).

The determination of GWP₁₀₀ is performed by combining experimental dataconcerning the atmospheric lifetime of the chemical compound and itsradiative efficiency with specific computational tool which are standardin the art and are described e.g. in the extensive review published byHodnebrog et. Al. in Review of Gephisics, 51/2013, p 300-378. Highlystable halogenated molecules such as CF₄ and chloro/fluoro alkanes havea very high GWP₁₀₀ (7350 for CF₄, 4500 for CFC-11).

Over the years heat transfer fluids having elevated values of GWP (suchas the chloro/fluoro alkanes used in air conditioning systems) have beenphased out by the industry and replaced with compounds having a lowerGWP₁₀₀ value and there is still a continuous interest in heat transferfluids having GWP₁₀₀ values which are as low as possible.

Hydrofluoroethers, in particular segregated hydrofluoroethers, tend tohave relatively low GWP₁₀₀ values while the rest of their properties canbe compared to those of the CFCs used in the past, for this reason somehydrofluoroethers have been used industrially and gained popularity asheat transfer fluids and are marketed e.g. by 3M under the trade name“Novec®”.

Hydrofluoroethers are broadly described as heat transfer media due totheir wide temperature range where they are liquid, and due to their lowviscosity in a broad range of temperatures which makes them useful forapplications as low temperature secondary refrigerants for use insecondary loop refrigeration systems where viscosity should not be toohigh at operating temperatures.

Fluorinated ethers are described for example by 3M in U.S. Pat. No.5,713,211, by Dupont in US 2007/0187639 and by Solvay Solexis in WO2007/099055 and WO2010034698.

However, while much lower than CFCs, the GWP₁₀₀ of segregatedhydrofluoroethers is still in a range from 70 to 500 as shown in U.S.Pat. No. 5,713,211 (table 5):

GWP₁₀₀ C₄F₉—O—CH₃ 330 C₄F₉—O—C₂H₅ 70 c-C₆F₁₁—O—CH₃ 170

Other hydrofluoro-olefins have been commercialized as heat transferfluids e.g. by Chemours (Opteon™) and Honeywell (Solstice™). Thesecompounds have a very low GWP, around 1, but, differently from theformerly cited compounds, are much more flammable and therefore thislimits their field of use.

Therefore there is still a need to develop methods for effective heattransfer using heat transfer fluids which have good thermal anddielectric properties, are liquid in a broad range of temperatures, arenon flammable, and have very low GWP₁₀₀ (30 and below).

SUMMARY OF INVENTION

The present invention relates to a method for exchanging heat with anobject said method comprising using a heat transfer fluid wherein saidheat transfer fluid comprises one or more chemical compounds having thegeneral formula:

wherein:

-   -   R_(f) can be any C₁-C₁₀ fluorinated linear or branched carbon        chain which can be partially or fully fluorinated, and can        comprise O or S atoms,    -   X, Y and Z can be independently selected from halogens or        hydrogen, with the provision that at least one of X, Y or Z is a        halogen.

DESCRIPTION OF EMBODIMENTS

For “electronic computing equipment” it is intended any individual orarrays of individual computer boards comprising microprocessors CPUs,GPUs, SSD and DDR Memory, and performing computational work, thusincluding both large server farms, internet servers, bitcoin miningfactories, but also smaller individual computers, internet servers,computer gaming equipment. Both large and small installation may benefitfrom the heat transfer method of the present invention.

The term “semiconductor device” in the present invention include anyelectronic device which exploits the properties of semiconductormaterials. Semiconductor devices are manufactured both as single devicesand as integrated circuits which consist of a number (which can go fromtwo to billions) of devices manufactured and interconnected on a singlesemiconductor substrate or “wafer”. The term “semiconductor devices”includes both the basic building blocks, such as diodes and transistors,to the complex architectures built from these basic blocks which extendto analog, digital and mixed signal circuits, such as processors, memorychips, integrated circuits, circuit boards, photo and solar cells,sensors and the like. The term “semiconductor devices” also includes anyintermediate or unfinished product of the semiconductor industry derivedfrom a semiconductor material wafer.

The present invention relates to a method for exchanging heat with anobject said method comprising using a heat transfer fluid wherein saidheat transfer fluid comprises one or more chemical compounds having thegeneral formula:

wherein:

-   -   R_(f) can be any C₁-C₁₀ fluorinated linear or branched carbon        chain which can be partially or fully fluorinated, and can        comprise O or S atoms,    -   X, Y and Z can be independently selected from halogens or        hydrogen, with the provision that at least one of X, Y or Z is a        halogen.

Preferably X, Y and Z can be independently selected from F, Cl, Br orhydrogen with the provision that at least one of X, Y or Z is F, Cl orBr.

More preferably at least one of X, Y or Z is Cl or Br, even morepreferably X is selected from H and Cl, Y and Z are selected from Cl orF. Most preferably one of Y and Z is F and the other is Cl, while X isCl.

In all embodiments it is preferred that R_(f) is a fully fluorinatedlinear or branched carbon chain optionally comprising O or S atoms, morepreferably R_(f) is a C₁ carbon chain, even more preferably is CF₃

The most preferred compound among those encompassed by the generalformula (I) is CF₃OCCl═CFCl, i.e.1,2-dichloro-1-fluoro-2-(trifluoromethoxy)-ethene (DCFTFME).

The method of the invention can be used to exchange heat with anyobject. The method of the invention is particularly useful when theobject is an electronic computing equipment such as e.g. computerservers. In fact the method of the present invention employs heattransfer fluids which are dielectric and non corrosive so that it canalso be used in systems using the so called “immersion cooling” or“direct contact cooling”. In these systems the fluids are placed indirect contact with the electronic circuit boards. Such fluids at theirworking temperature can be gaseous, liquids (single phase immersioncooling) or be in a gas/liquid equilibrium (i.e. around the boilingpoint of the liquid, in the so called “two phase immersion cooling”).

In immersion cooling, electronic computer equipment such as CPUs, GPUs,Memory, and other electronics, including complete servers, arecompletely immersed in a thermally conductive dielectric liquid orcoolant, which temperature is controlled through the use of acirculation system which pumps the liquid trough pipes and to heatexchangers or to radiator type coolers to reject the heat from thecoolant.

Server immersion cooling is becoming a popular solution for servercooling solution, as it allows to drastically reduce energy usagethrough the elimination of the expensive air conditioninginfrastructure. These systems are replaced with efficient low speedliquid circulation pumps and simpler heat exchanger and/or radiatorsystems.

The temperatures used in liquid immersion cooling are determined by thehighest temperature at which the devices being immersed can reliablyoperate. For servers this temperature range is typically between 15 to65° C., however in some cases this range is extended up to 75° C.

Current commercial applications for immersion cooling range from datacenter oriented solutions for commodity server cooling, server clusters,HPCC applications and Bitcoin Mining and mainstream cloud-based and webhosting architectures. Liquid immersion cooling is also used in thethermal management of computing equipment related to LEDs, Lasers, X-Raymachines, and Magnetic Resonance Imaging devices.

The method of the present invention is suitable for both single phaseimmersion cooling and two phase immersion cooling. Among the compoundsof the invention according to the general formula (I) those having alonger R_(f) chain (typically from C3 and above, see below examples 4, 5in the examples section below) exist as liquids in a broad range oftemperatures and are therefore suitable for open bath systems where theheat exchange composition remains liquid in all phases of operation.Typically the heat transfer fluid is pumped to an external heatexchanger where it is cooled (or heated in case of need) andrecirculated into the bath. A more or less sophisticated control systemmay be present controlling the instant temperature of the fluid and thetemperature of the servers optimizing the fluid temperature in eachmoment. The low vapour pressure of the compounds with longer Rf chainsallows to minimize evaporation and loss of the compounds.

On the contrary compounds of the invention according to the generalformula (I) those having a shorter R_(f) chain (in particular thosehaving a C1-C3 R_(f) such as for example those in Examples 1, 2, 6 and 7in the examples section below) have relatively low boiling points in arange from 20° C. to 80° C.

These low boiling compounds may be used in the so called “two phaseimmersion cooling”. Two phase immersion cooling is a technology marketedby Allied Control and a few other players, which involve submerging theelectronic devices in closed tanks with a bath of dielectric fluid wherethe dielectric fluid has a boiling point corresponding to a desiredtemperature at which the bath can be set. When the electronic devicesheat up to the boiling point of the dielectric fluid the fluid turnsinto vapor subtracting heat. The vapor then condenses on a lid or coilcondenser placed above the bath and precipitates again in the bath. Adesign of this type is particularly appreciated because it does notrequire recirculation of the dielectric fluid, and allows packing moreelectronic devices is a small space.

Still in the field of computer equipment cooling, the method of theinvention can also be used in non immersion cooling system where theheat exchange fluid is circulated in a closed system and brought inthermal contact with the processors trough plates of thermallyconductive materials, such as the server cooling solutions produced byEbullient under the name of “module loops”. The use of a dielectricfluid is anyway beneficial because the risk of leakages is alwayspresent and conductive liquids may have destructive effects on theelectronics.

The method of the invention can also find application for example in thesemiconductor industry where temperature control during manufacturing ofsemiconductor devices is of great importance. In this case the objectwhich exchanges heat with the heat transfer fluid is a semiconductordevice. Temperature control units (TCUs) are used all along theproduction line for the fabrication of semiconductor devices, and useheat transfer fluids to remove unwanted heat during steps like waferetching and deposition processes, ion implantation and lithographicprocesses. The heat transfer fluid is typically circulated through thewafer mounts and each process tool which requires temperature controlhas its own individual TCU.

Some tools of particular importance which include TCUs are silicon waferetchers, steppers and ashers. Etching is performed using reactive plasmaat temperatures ranging from 70° C. to 150° C. and the temperature ofthe wafer must be controlled precisely with the entire temperaturerange.

Steppers are used in the photolithography of wafers to form thereticules which are then used to expose the photosensitive mask. Thisprocess is carried out at temperatures between 40° C. and 80° C.,however temperature control is extremely important as the wafer need tobe maintained at a precise fixed temperature (+/−0.2° C.) along theprocess to ensure good results.

Ashing is a process where the photosensitive mask is removed from thewafer and is performed at temperatures from 40° C. to 150° C. The systemuses plasma and also here precise temperature control is particularlyimportant.

Another relevant process is plasma enhanced chemical vapour deposition(PECVD) wherein films of silicon oxide, silicon carbide and/or siliconnitride are grown on a wafer within a chamber. Also in this case, whilethe temperature at which this step is performed can be selected in therange between 50° C. and 150° C., during the deposition process thewafer must be kept uniformly at the selected temperature.

In a semiconductor device production facility typically each Etcher,Asher, Stepper and plasma enhanced chemical vapour deposition (PECVD)chamber has its own TCU wherein a heat transfer fluid is recirculated.

Another process step where heat transfer fluids are used in themanufacturing of semiconductor devices is vapour phase reflow (VPR)soldering. This is the most common method used to connect surface mountdevices, multi chip modules and hybrid components to circuit boards. Inthis method the soldering material is applied in paste form and then thesemiconductor device e.g. an unfinished circuit board is placed in aclosed chamber with heat transfer fluid at its boiling point inequilibrium with its vapour phase. The fluid in vapour phase transfersheat to the soldering paste which then melts and stabilize the contacts.In this case the fluid is in direct contact with the circuit board sothat it must be dielectric and non corrosive. For this application isimportant that the heat transfer fluid comprises compounds having aboiling point which is sufficient to melt the soldering paste.

Another system which is a key part of the production process of manysemiconductor devices is thermal shock testing. In thermal shock testinga semiconductor device is tested at two very different temperature.Different standards exist, but in general the test consists insubjecting the semiconductor device to high and low temperatures andthen testing the physical and electronic properties of the device.Typically the semiconductor device to be tested is directly immersedalternatively in a hot bath (which can be at a temperature of from 60°C. to 250° C.) and a cold bath (which can be typically at a temperatureof from −10° C. to −100° C.). The transfer time between the two bathmust be minimized, generally below 10 seconds. Also in this test thefluid making up the baths goes in direct contact with the device andtherefore must be dielectric and non corrosive. In addition, to avoidcontamination of the baths, it is highly preferable that the same fluidis used both in the cold and in the hot bath. Therefore heat transferfluids which exist as liquid in a broad range of temperatures arepreferred.

Heat transfer fluids for use in the manufacturing of semiconductordevices are typically liquids which are dielectric, non corrosive, andexist in the liquid state in a broad range of temperatures withrelatively low viscosity which makes them easily pumpable.

The method of the invention can be used in all the steps of themanufacturing of semiconductor devices which require the semiconductordevice to exchange heat with a heat transfer fluid. In particular whenusing semiconductor processing equipment such as an Etcher, an Asher, aStepper and a plasma enhanced chemical vapour deposition (PECVD)chamber, each one of these equipment requires precise temperaturecontrol and/or heat dissipation and therefore they include temperaturecontrol units (TCUs) which can include the selected heat transfer fluidof the method of the invention.

Additionally in thermal shock testing, which is an integral part ofsemiconductor device manufacturing because only those devices which passthe test are processed further, the semiconductor device is cooled andheated using at least two baths made of heat transfer fluids, a cold onetypically at a temperature of from −10 to −100° C., and a hot onetypically at a temperature of from 60° C. to 250° C. The method of theinvention can be advantageously used selecting the appropriate compoundor blend of compounds according to the general formula (I) for making upthe heat transfer fluid for the baths. Preferably the heat transferfluid should be selected so that the same heat transfer fluid can beused in both bath thanks to the large temperature range in which thefluid is in liquid state, so that there is no risk of crosscontamination of the baths. In this case compounds according to thegeneral formula (I) and having as R_(f)C3-C10 chains are preferred.

The method of the invention can also find application in vapor phasesoldering, in fact the selected heat transfer fluid of the method of theinvention can be formulated so to have a boiling point in line with thatof the soldering paste, so that a semiconductor device comprisingsoldering paste which still has to be “cured” can be introduced into aclosed chamber which contains the selected heat transfer fluid of themethod of the invention at its boiling point in equilibrium with itsheated vapors. The heated vapors will transfer heat to the semiconductordevice thereby melting the soldering paste and therefore fixing thecontacts as needed. For this application high boiling point compoundsaccording to the general formula (I) will need to be used in the heattransfer fluid, compounds according to the general formula (I) andhaving as R_(f) C4-C10 chains are preferred for their higher boilingpoint.

An additional advantage is that a single heat transfer fluid can be usedin multiple applications potentially allowing the use of a single heattransfer fluid across an entire semiconductor devices manufacturingfacility.

Another area wherein the method of the present invention can findapplication is the thermal management of batteries, in particularrechargeable batteries such as vehicle batteries for cars, trams, trainsand the like.

Currently, most of the development in the field of rechargeablebatteries, in all industry segments, is focused on Lithium-ion basedbatteries which are based on different types of lithium salts. Batteriesbased on Lithium Manganese Oxide, Lithium Iron Phosphate and LithiumNickel Manganese Cobalt Oxide find application e.g. in vehicles, powertools, e-bikes, and the like. Batteries based on Lithium Cobalt Oxideare typically used in smaller sizes and less intensive applications suchas cell phones, portable computers and cameras. Batteries based onLithium Nickel Cobalt Aluminum Oxide and Lithium Titanate are beingconsidered in applications requiring high power and/or capacity such aselectric powertrain and grid storage. Naturally also new technologies,outside the realm of Lithium-ion based batteries, are being explored andcontinuously developed. The method of the present invention is notlinked to a particular battery technology and is applicable to bothcurrent and future generations of battery systems.

Differently from conventional power systems, batteries, and inparticular rechargeable batteries, have strict requirements for theirworking environment. Batteries tend to operate in the best conditionswithin a relatively narrow range of temperatures.

In general low temperatures have an effect on the battery chemistryslowing down the reaction rate and therefore reducing the electricityflow when charging or discharging. High temperatures increase thereaction rate and at the same time also increase energy dissipation thusgenerating even more excess heat possibly causing an uncontrolledincrease of Temperature which can cause irreversible damage to the cell.For a typical Li-ion battery a temperature above 80° C., even only in apart of its structure, can start exothermal chemical reactions whichcause a further temperature increase of the battery, ultimately leadingto a complete collapse of the battery with risk of fire and explosion.

On the other hand, the practical applications of batteries require themto be efficient in a much broader range of temperatures. For examplevehicles batteries need to function properly in any environment wherepeople is expected to use them, so that they need to be operative in atemperature range from −20° C. to +40° C. and beyond. In addition tothat, charge and discharge cycles of batteries can generate heat withinthe battery itself making it even more difficult to maintain the batterywithin an acceptable temperature range.

Indicative figures for a typical Li-ion battery suggest that the usablerange is normally from −20° C. to 60° C., but a good power output isonly obtained from 0° C. to 40° C., where optimal performance is onlyobtainable from 20° to 40° C. Temperature also affects battery duration,in fact the number of charge/discharge cycles a battery can withstandbefore being considered exhaust go down quickly below 10° C. due toanode plating, and above 60° C. due to the deterioration of theelectrode materials. The temperature ranges for optimal performance maybe different for different battery chemistries and constructions,however all current commercial batteries share a relatively narrowtemperature window where their performance is optimal. It is alsoimportant in general to ensure that the entire battery is kept uniformlyat the same temperature without hot or cold zones, as this can reduceits lifetime and safety.

For this reason it is nowadays standard to integrate a Battery Thermalmanagement System (BTMS) within commercial battery assemblies,especially when safety, reliability and lifetime of the battery are asignificant concern. These BTMSs can be more or less complex, dependingon the type of battery, however one common element is the presence of aheat transfer fluid such as a gas or a liquid which exchanges heat withthe battery thus heating or cooling it.

Battery thermal management systems (BTMSs) are therefore extremelyimportant, especially in applications requiring high power, and highreliability such as vehicles batteries. A BTMS can be more or lesscomplex, depending on the application, but each BTMS has at least afunction to cool the battery when its temperature is too high and afunction to heat the battery when its temperature is too low, typicallyusing a heat transfer fluid which exchanges heat with the battery. Othercommon features in BTMSs are an insulation system, to reduce the effectof the external environment on the battery temperature, and aventilation system which helps dissipating hazardous gases which maydevelop within the battery pack. However the method of the presentinvention relates specifically to the heat exchange function of a BTMSand can be applied easily to any BTMS and integrated with its otherfunctions and features.

BTMSs using a liquid as heat transfer fluid are common because liquidscan transfer a larger amount of heat more quickly than gases. Typicallythe fluid is circulated by a pump within a closed system which is inthermal contact with the battery and with a second system which has thefunction of heating and/or cooling the fluid to the desired temperature.This second system may comprise any combination of a refrigerationsystem and a heating system or may combine heating and cooling functionsin a heat pump. The circulating fluid absorbs heat from or release heatto the battery and then it is circulated in said second system to bringthe fluid back to the desired temperature. A more or less sophisticatedcontrol system may be present controlling the instant temperature of thefluid and the temperature of the battery optimizing the fluidtemperature in each moment.

In some systems the fluid which is circulated in the system can go indirect contact with the battery cells which are then immersed in it.Clearly in these cases the fluid must be dielectric in order to protectthe battery cells and their electronic components. In other cases theheat transfer fluid is circulated in a separate closed system which onlyexchanges heat by indirect contact trough e.g. a heat exchange platemade of metal or other thermally conductive material. A dielectric fluidmay be beneficial also in this type of systems because closed systemshave anyway a high risk of leakages.

Particularly for high power batteries thermal management systems basedon fluids, liquids in particular, are being used and the method of theinvention offers an improved thermal management at a lowered GWP₁₀₀.

Beyond the cited applications, the method of the invention can be alsoadapted to any heat exchange method e.g. for heating or coolingcompartments (e.g. food stuffs compartments) including those on board ofaircrafts, vehicles or boats, for heating or cooling industrialproduction equipment, for heating or cooling batteries during theiroperations, for forming thermostatic baths.

As mentioned in the introduction, heat transfer fluids used in thesefields include fluorocompounds. In particular hydrofluorotethers havefound application in these fields due to their chemical inertness,dielectricity, wide range of T in which they are liquid and pumpable(typically having a viscosity between 1 and 50 cps at the temperaturesof use), low flammability and relatively low GWP.

Commercially available hydrofluoroethers for use in these fields aree.g. those from the Novec™ series of 3M which combine all theseproperties with a relatively low GWP₁₀₀ of from about 70 to 300.

Still, GWP is a critical property nowadays also due to the regulatoryenvironment so that there is always a demand to develop new heatexchange fluids which have even lower GWP than then currentlycommercialized hydrofluoroethers.

The applicant has surprisingly found that the heat transfer fluidemployed in the method of the invention is non-flammable, providesefficient heat transfer, can be used across a wide temperature range andhas equal or improved dielectric properties with respect to otherhydrofluoroethers commercialized as heat transfer fluids. Surprisinglyheat transfer fluids used in the invention have an extremely low GWP₁₀₀,in general lower than 30 and for some materials even lower than 3, as itwill be shown below in the experimental section. This is a particularlyunexpected result and in fact previous reviews such as Hodnebrog et. al.cited above did not investigate or propose fluorinated vinyl ethercompounds as low GWP compounds.

Therefore, using these selected chemical compounds in accordance to thegeneral formula (I) heat transfer fluids can be formulated which have aGWP100 value of less than 30, preferably less than 10, even morepreferably less than 5. The heat transfer fluids according to theinvention also have low toxicity, showing good heat transfer propertiesand relatively low viscosity across the whole range. Also, the fluids ofthe invention have good electrical compatibility, i.e. they are noncorrosive, have high dielectric strength, high volume resistivity andlow solvency for polar material. The electrical properties of the fluidsof the invention are such that they can be used in immersion coolingsystem for electronics in direct contact with the circuits as well as inindirect contact applications using loops and/or conductive plates.

The heat transfer fluids for use in the method of invention preferablycomprise more than 5% by weight of one or more compounds according toformula (I) above, more preferably more than 50% by weight, even morepreferably more than 90% by weight. In one embodiment the heat transferfluid is entirely made of one or more compounds according to the generalformula above.

In some embodiments the heat transfer fluid of the invention comprises ablend of chemical compounds according to formula (I).

The method of the invention can be applied to any heating and/or coolingsystem which uses an heat transfer fluid and in particular to all thoseexemplified in the description. Particularly for the temperature controlof electronic computing equipment, both in immersion cooling of suchequipment, where the electronic circuit boards are directly immersed inthe liquid, to distributed systems where the fluids are distributed tocooling elements capable of exchanging heat with boards such as platesof thermally conductive materials such as metals and metallic alloys.

Other applications are in the thermal management of batteries,particularly rechargeable batteries, e.g. for vehicles such as cars,trams, trains.

Further applications are found in the semiconductor industry where theobject of the heat exchange is a semiconductor device, such as intemperature control units (TCUs) for etchers, ashers, steppers and PECVDchambers, in thermostatic baths for thermal shock testing and in vaporphase soldering.

In another aspect the present invention also encompasses an apparatuscomprising an electronic computing equipment and a heat transfer fluidwherein said heat transfer fluid comprises one or more chemicalcompounds having the general formula (I).

In a further aspect the present invention relates to an apparatuscomprising a battery, preferably a rechargeable battery, a thermalmanagement system for said battery, said thermal management system forsaid battery comprising a heat transfer fluid exchanging heat with saidbattery, wherein said heat transfer fluid comprises one or more chemicalcompounds having the general formula (I).

Should the disclosure of any patents, patent applications, andpublications which are incorporated herein by reference conflict withthe description of the present application to the extent that it mayrender a term unclear, the present description shall take precedence.

The invention will be now described in more detail with reference to thefollowing examples whose purpose is merely illustrative and notlimitative of the scope of the invention.

Standards:

Measurement of electrical properties were performed according to thefollowing standards:

Volume resistivity—ASTM D5682-08[2012]

Dielectric strength—ASTM D877/D877M-13

Dielectric constant—ASTM D924-15

EXAMPLES Example 1—Synthesis of CF₃OCCl═CFCl Step 1—Addition of CF₃OF toTrichloroethylene (TCE)

100 g of the ether CF₃OCFClCF₂Cl as solvent and 5.0 g of TCE have beenintroduced in a 100 cc stainless steel reactor, equipped with amechanical stirrer. The reactor was then cooled to −50° C. with acryogenic bath. Through a bubbling inlet 43.5 g of TCE as gas were fedin the reactor in 10 hours, by a pump and contemporarily, throughanother bubbling inlet, a total of 0.89 mol of trifluoromethylhypofluorite (which can be obtained from COF₂ and F₂ following theteaching of U.S. Pat. No. 4,900,872), diluted with helium in a molarratio He/CF₃OF=2.0. The molar ratio CF₃OF/TCE is equal to 1.5 and CF₃OFwas added at 0.089 mol/h. At the end of the reaction 185.7 g of mixturewere discharged. The mixture contained CF₃OCHClCCl₂F and CF₃OCCl₂CHClFin molar ratio 95/5, the yield for both compounds was 96% in moles.

Step 2—Dehydrochlorination of CF₃OCHClCCl₂F and CF₃OCCl₂CHClF

60 g of the mixture obtained in Step 1 and 5.0 g of tetrabutylammoniumhydroxide in aqueous solution 40% by weight were introduced in a 250 ccfour-necked glass reactor equipped with a magnetic stirrer, droppingfunnel, thermometer and water condenser. Then 20.5 g of NaOH in aqueoussolution at 20% by weight were added under vigorous stirring: thetemperature was maintained at about 35° C. with a H₂O/ice bath. Afterthe completion of the NaOH addition the mixture was stirred foradditional 30 minutes. The mixture, at the end of the reaction, wascooled to 20° C. and poured in a separator funnel: two phases werepresent and the organic bottom phase (47.7 g) was separated anddistilled through a fractional column. CF₃OCCl═CFCl (boiling point 55°C.), pure at 99.9% by moles was obtained. Yield for step 2 was 93% inmoles.

Example 2—Synthesis of CF₃CF₂OCCl═CFCl Step 1—Addition of CF₃CF₂OF totrichloroethylene (TCE)

Following the same procedure and equipment of “Example 1—Step 1”, 100 gof CF₃OCFClCF₂Cl ether as solvent and 5.0 g of TCE were introduced inthe reactor. Then, at −70° C., 43.5 g of TCE were fed in the reactor in10 hours, by a pump and contemporarily 0.89 moles of pentafluoroethylhypofluorite CF₃CF₂OF were fed in 10 hours (the hypofluorite can beobtained from CF₃COF and F₂ following the teaching of U.S. Pat. No.4,900,872) diluted with helium in a molar ratio He/CF₃CF₂OF=10. Theresulting molar ratio CF₃CF₂OF/TCE was equal to 1.4 and CF₃CF₂OF wasadded at 0.089 mol/h.

The resulting mixture (205.0 g) contained two reaction products:CF₃CF₂OCHClCCl₂F and CF₃CF₂OCCl₂CHClF. The yield in the two additionproducts was 62% in moles.

Step 2—Dehydrochlorination of CF₃CF₂OCHClCCl₂F and CF₃CF₂OCCl₂CHClF

60 g of the mixture obtained in the Step 1 and 5.0 g oftetrabutylammonium hydroxide in aqueous solution 40% by weight wereintroduced in a 250 cc four-necked glass reactor equipped with amagnetic stirrer, dropping funnel, thermometer and water condenser. Then17 g of NaOH in aqueous solution at 20% by weight were added undervigorous stirring: the temperature was maintained at about 35° C. with aH₂O/ice bath. After the completion of the NaOH addition the mixture wasstirred for additional 30 minutes.

The mixture, at the end of the reaction, was cooled to 20° C. and pouredin a separator funnel: two phases were present and the organic bottomphase (48.8 g) was separated and distilled through a fractional column.CF₃CF₂OCCl═CFCl (boiling point 73° C.), pure at 99.8% by moles wasobtained with a yield for step 2 of 93% in moles.

Example 3—Synthesis of CF₃CF₂CF₂OCCl═CFCl Step 1—Addition of CF₃CF₂CF₂OFto trichloroethylene (TCE)

Following the same procedure and equipment of “Example 1—Step 1”, 100 gof CF₃OCFClCF₂Cl ether as solvent and 5.0 g of TCE were introduced inthe reactor. Then, at −80° C., 43.5 g of TCE were fed in the reactor in10 hours, by a pump and contemporarily 0.89 moles of heptafluoropropylhypofluorite CF₃CF₂CF₂OF were fed in 10 hours (the hypofluorite can beobtained from CF₃CF₂COF and F₂ following the teaching of U.S. Pat. No.4,900,872) diluted with helium in a molar ratio He/CF₃CF₂CF₂OF=10. Theresulting molar ratio CF₃CF₂CF₂OF/TCE was equal to 1.4 and CF₃CF₂CF₂OFis added at 0.089 moles/h.

The resulting mixture (230.0 g) contained two reaction products:CF₃CF₂CF₂OCHClCCl₂F and CF₃CF₂CF₂OCCl₂CHClF. The yield in the twoaddition products was 40%.

Step 2—Dehydrochlorination of CF₃CF₂CF₂OCHClCCl₂F andCF₃CF₂CF₂OCCl₂CHClF

50 g of the mixture obtained in the Step 1 and 4.0 g oftetrabutylammonium hydroxide in aqueous solution 40% by weight wereintroduced in a 250 cc four-necked glass reactor equipped with amagnetic stirrer, dropping funnel, thermometer and water condenser. Then15 g of NaOH in aqueous solution at 20% by weight were added undervigorous stirring: the temperature was maintained at about 35° C. with aH₂O/ice bath. After the completion of the NaOH addition the mixture wasstirred for additional 30 minutes.

The mixture, at the end of the reaction, was cooled to 20° C. and pouredin a separator funnel: two phases were present and the organic bottomphase (48.8 g) was separated and distilled through a fractional column.CF₃CF₂CF₂OCCl═CFCl (boiling point 93° C.), pure at 99.8% by moles wasobtained. Yield for step 2 was 92% in moles.

Example 4—Synthesis of (CF₃)₂CFCF₂OCCl═CFCl Step 1—Addition of(CF₃)₂CFCF₂OF to trichloroethylene (TCE)

Following the same procedure and equipment of “Example 1—Step 1”, 100 gof CF₃OCFClCF₂Cl ether as solvent and 5.0 g of TCE were introduced inthe reactor. Then, at −80° C., 23 g of TCE were fed in the reactor in 10hours, by a pump and contemporarily 0.45 moles of nonafluoroisobutirroylhypofluorite (CF₃)₂CFCF₂OF were fed in 10 hours (the hypofluorite can beobtained from (CF₃)₂CFCF₂COF and F₂ following the teaching of U.S. Pat.No. 4,900,872) diluted with helium in a molar ratio He/(CF₃)₂CFCF₂OF=15.The resulting molar ratio (CF₃)₂CFCF₂OF/TCE was equal to 1.5 and(CF₃)₂CFCF₂OF was added at 0,045 moles/h.

The resulting mixture (181.0 g) contained two reaction product:(CF₃)₂CFCF₂OCHClCCl₂F and (CF₃)₂CFCF₂OCCl₂CHClF. The yield in the twoaddition products was 20%.

Step 2—Dehydrochlorination of (CF₃)₂CFCF₂OCHClCCl₂F and(CF₃)₂CFCF₂OCCl₂CHClF

20 g of the mixture obtained in the Step 1 and 2.0 g oftetrabutylammonium hydroxide in aqueous solution 40% by weight wereintroduced in a 250 cc four-necked glass reactor equipped with amagnetic stirrer, dropping funnel, thermometer and water condenser. Then15 g of NaOH in aqueous solution at 20% by weight were added undervigorous stirring: the temperature was maintained at about 35° C. with aH₂O/ice bath. After the completion of the NaOH addition the mixture wasstirred for additional 30 minutes.

The mixture, at the end of the reaction, was cooled to 20° C. and pouredin a separator funnel: two phases were present and the organic bottomphase (17.1 g) was separated and distilled through a fractional column.(CF₃)₂CFCF₂OCCl═CFCl (boiling point 113° C.), pure at 99.8% by moles wasobtained. Yield for step 2 was 96% in moles.

Example 5—Synthesis of CF₃CF₂OCF₂CF₂OCF₂CF₂OCCl═CFCl Step 1:Fluorination of CF₃CF₂OCF₂CF₂OCF₂COF in the Presence of CHCl═CCl₂

40 g of CF₃OCFClCF₂Cl ether as solvent, 20 g of CF₃CF₂OCF₂CF₂OCF₂C(O)F,(prepared as described in U.S. Pat. No. 9,416,085) and 50 g of TCE wereintroduced in the same reactor of Example 1. The reaction mixture wasmaintained at −75° C. and 0.067 moles/h of fluorine diluted with helium(F₂/He 1/5 in moles) were fed therein for 5 hours. The mixture obtainedhas been distilled through a 60 plates Spalthror Fischer distillationapparatus. 20.5 g of CF₃CF₂OCF₂CF₂OCF₂CF₂OCHClCCl₂F andCF₃CF₂OCF₂CF₂OCF₂CF₂OCCl₂CHClF were obtained with a combined yield of69% in moles.

Step 2 Dehydrochlorination of CF₃CF₂OCF₂CF₂OCF₂CF₂OCHClCCl₂F andCF₃CF₂OCF₂CF₂OCF₂CF₂OCCl₂CHClF

20 g of the compounds obtained in Step 1 and 2.0 g of tetrabutylammoniumhydroxide in aqueous solution 40% by weight were introduced in a 250 ccfour-necked glass reactor equipped with a magnetic stirrer, droppingfunnel, thermometer and water condenser. Then 5 g of NaOH in aqueoussolution at 20% by weight were added under vigorous stirring: thetemperature was maintained at about 35° C. with a H₂O/ice bath. Afterthe completion of the NaOH addition the mixture was stirred foradditional 30 minutes.

The mixture, at the end of the reaction, was cooled to 20° C. and pouredin a separator funnel: two phases were present and the organic bottomphase (18.5 g) was separated and distilled through a fractional column.The distilled product consists of CF₃CF₂OCF₂CF₂OCF₂CF₂OCCl═CFCl (boilingpoint 150° C.), pure at 99.8% molar. Yield for step 2 was 96% in moles.

Example 6—Synthesis of CF₃OCH═CHF Step 1: Addition of CF₃OF to 1,2dichloroethylene (DCE)

Following the same procedure and equipment of “Example 1—Step 1”, 100 gof CF₃OCFClCF₂Cl ether as solvent and 5.0 g of DCE were introduced inthe reactor. Then, at −80° C., 40 g of DCE were fed in the reactor in7.5 hours, by a pump and contemporarily 0.67 moles of trifluoromethylhypofluorite CF₃OF were fed in 7.5 hours (the hypofluorite can beobtained from COF₂ and F₂ following the teaching of U.S. Pat. No.4,900,872) diluted with helium in a molar ratio He/CF₃OF=5. Theresulting molar ratio CF₃OF/DCE was equal to 1.5 and CF₃CF₂OF was addedat 0.089 mol/h. The resulting mixture (192.0 g) contains CF₃OCHClCHClF.Yield was 96%.

Step 2: Dechlorination of CF₃OCHClCHClF

100 ml of dimethylformamide (DMF), 20 g of Zn powder and 2 g of ZnCl₂were placed in a 250 cc three-necked glass reactor equipped with amagnetic stirrer, dropping funnel, thermometer and connected through aVigreaux column and a water condenser to a cold trap at −75° C. Thetemperature of the reactor was brought to 65° C. and 50 g ofCF₃OCHClCHClF were added dropwise under mechanical agitation. After theaddition, the mixture was stirred for an additional hour.

27.8 g mixture were collected in the cold trap. The 1H and 19F NMRconfirm the presence of the product CF3OCH═CHF (boiling point 15° C.)pure at 99.6%. Yield for step 2 was 86% in moles.

Example 7—Synthesis of CF₃OCH═CClF and CF₃OCCl═CHCF Step 1: Same as Step1 of Example 1 Step 2: Dehydrochlorination of CF₃OCHClCCl₂F andCF₃OCCl₂CHClF

100 ml of dimethylformamide (DMF), 25 g of Zn powder and 2 g of ZnCl₂were placed in a 250 cc three-necked glass reactor equipped with amagnetic stirrer, dropping funnel, thermometer and connected through aVigreaux column and a water condenser to a cold trap at −75° C. Thetemperature of the reactor was brought to 75° C. and 60 g of the mixtureobtained in Step 1 (containing CF₃OCHClCCl₂F and CF₃OCCl₂CHClF in molarratio 95/5) were added dropwise under mechanical agitation. After theaddition, the mixture was stirred for an additional hour. 34.0 g werecollected in the cold trap. The 1H and 19F NMR confirm the presence oftwo products CF₃OCH═CClF and CF₃OCCl═CHCF in a molar ratio 95/5. Yieldfor step 2 was 81% in moles. The two compounds were then separated viadistillation with a 10 plates column. CF₃OCH═CClF (boiling point 20° C.)is obtained pure at 99.7% molar.

GWP Measurement

The GWP₁₀₀ for 1,2-dichloro-1-fluoro-2-(trifluoromethoxy)-ethene(DCFTFME) has been determined at the University of Oslo according toestablished procedures, by measuring the integrated absorption crosssection of infrared spectra over the region 3500-400 cm⁻¹, the kineticof reaction with OH radicals, and calculating the consequent atmosphericlifetime and radiative forcing efficiency. As a result of thesemeasurements a GWP₁₀₀ of 2.6 has been obtained.

Data relevant to GWP₁₀₀ measurement for DCFTFME:

Integrated absorption cross section at 3500-400 cm⁻¹:

36.6*10{circumflex over ( )}−17 cm² molecule⁻¹ cm⁻¹

Radiative forcing efficiency (calc)=0.435 W m⁻²

OH radicals kinetic k_(DCFTFME+OH)=5×10⁻¹³ cm³ molecule⁻¹ s⁻¹ at 298K

Atmospheric lifetime of DCFTFME<1 month

GWP₁₀₀=2.6

Electric and thermal properties of in comparison with other commerciallyavailable hydrofluoroethers:

Volume Dielectric resistivity strength Dielectric GWP₁₀₀ (ohm cm−1) (kV)constant NOVEC 7200 70 1.00E+08 30 7.3 NOVEC 7000 530 1.00E+08 40 7.4DCTFME 2.6 2.00E+11 29 2.2

Other physical properties of compounds according to the invention:

DCTFME Dielectric constant @1 kHz 2.2 Dielectric strength kV 29 Volumeresistivity Ohm*cm 2.00E+11 heat capacity cal/g° C., 0.19 viscosity (25°C.) cSt, 0.3 density (25° C.) g/cm3, 1.53 heat of vaporization kcal/kg32 surface tension mN/m pour point ° C. −105 Boiling point ° C. 55

The results show how the compounds of the invention have overall equalor improved properties when compared with existing commercial materialsused for similar purposes and have lower GWP. Heat transfer fluidscomprising these compounds can be used in all the mentioned applicationsinvolving heat exchange with an electronic computing equipment,batteries or semiconductor devices.

1.-15. (canceled)
 16. A method for exchanging heat with an object saidmethod comprising using a heat transfer fluid wherein said heat transferfluid comprises one or more chemical compounds having the generalformula:

wherein: R_(f) is any C₁-C₁₀ fluorinated linear or branched carbon chainwhich can be partially or fully fluorinated, and can comprise O or Satoms, X, Y and Z are independently selected from halogens or hydrogen,with the proviso that at least one of X, Y or Z is a halogen.
 17. Themethod according to claim 16 wherein said one or more chemical compoundsof general formula (I) make up at least 5% by weight of said heattransfer fluid.
 18. The method according to claim 16 wherein said heattransfer fluid has a GWP₁₀₀ of less than
 30. 19. The method according toclaim 16 wherein said object is an electronic computing equipment. 20.The method according to claim 19 wherein said electronic computingequipment is one or more servers.
 21. The method according to claim 19wherein said electronic computing equipment comprises one or moreelectronic circuit boards, said method comprising the step of contactingdirectly said electronic circuit boards with said heat transfer fluid.22. The method according to claim 19, wherein the method is a singlephase immersion cooling method.
 23. The method according to claim 19,wherein the method is a two phase immersion cooling method.
 24. Themethod according to claim 16, wherein said object is a battery.
 25. Themethod according to claim 16, wherein said object is a semiconductordevice.
 26. The method according to claim 25 wherein one or more of asemiconductor processing equipment selected from an Etcher, an Asher, aStepper and a plasma enhanced chemical vapour deposition (PECVD)chamber, is used, said semiconductor processing equipment including atleast one temperature control unit (TCU) exchanging heat with saidsemiconductor device, wherein said TCU comprises a heat transfer fluid,said heat transfer fluid comprising one or more chemical compoundshaving the general formula:

wherein: R_(f) is any C₁-C₁₀ fluorinated linear or branched carbon chainwhich can be partially or fully fluorinated, and can comprise O or Satoms, X, Y and Z are independently selected from halogens or hydrogen,with the proviso that at least one of X, Y or Z is a halogen.
 27. Themethod according to claim 25 wherein said method is a method for thermalshock testing of semiconductor devices, said method comprising, in anyorder: i. cooling said semiconductor device to a temperature comprisedfrom −10° C. and −100° C., using a first bath being made of a heattransfer fluid and ii. heating said semiconductor to a temperaturecomprised from 60° C. and 250°, using a second bath being made of a heattransfer fluid, wherein one or both said first and second bath comprisea heat transfer said heat transfer fluid comprising one or more chemicalcompounds having the general formula:

wherein: R_(f) is any C₁-C₁₀, preferably C₃-C₁₀, fluorinated linear orbranched carbon chain which can be partially or fully fluorinated, andcan comprise O or S atoms, X, Y and Z are independently selected fromhalogens or hydrogen, with the provision that at least one of X, Y or Zis a halogen.
 28. The method according to claim 25 wherein said methodis a method for vapor phase soldering of semiconductor devices, saidmethod including i. providing a semiconductor device comprisingsoldering paste, ii. providing a closed chamber comprising a heattransfer fluid at its boiling point so that heated vapors of said heattransfer fluid are generated within said closed chamber iii. introducingsaid semiconductor device in said closed chamber, in contact with saidvapors of said heat transfer fluid thereby melting said soldering pasteby contact with said heated vapors said heat transfer fluid comprisingone or more chemical compounds having the general formula:

wherein: R_(f) is any C₁-C₁₀ fluorinated linear or branched carbon chainwhich can be partially or fully fluorinated, and can comprise O or Satoms, X, Y and Z are independently selected from halogens or hydrogen,with the provision that at least one of X, Y or Z is a halogen.
 29. Anapparatus comprising an electronic computing equipment and a heattransfer fluid wherein said heat transfer fluid comprises one or morechemical compounds having the general formula:

wherein: R_(f) is any C₁-C₁₀ fluorinated linear or branched carbon chainwhich can be partially or fully fluorinated, and can comprise O or Satoms, X, Y and Z is independently selected from halogens or hydrogen,with the provision that at least one of X, Y or Z is a halogen.
 30. Anapparatus comprising a battery, a thermal management system for saidbattery, said thermal management system for said battery comprising aheat transfer fluid exchanging heat with said battery, wherein said heattransfer fluid comprises one or more chemical compounds having thegeneral formula:

wherein: R_(f) is any C1-C₁₀ fluorinated linear or branched carbon chainwhich can be partially or fully fluorinated, and can comprise O or Satoms, X, Y and Z is independently selected from halogens or hydrogen,with the provision that at least one of X, Y or Z is a halogen.